What is a Cell Membrane?

Cell membranes are mainly elastic semipermeable membranes made of phospholipids with a thickness of 7 to 8 nm. For animal cells, the outside of the membrane is in contact with the external environment. Its main function is to selectively exchange substances, absorb nutrients, excrete metabolic waste, and secrete and transport proteins. ^[1]

Cell membrane

Cell membranes are mainly elastic semipermeable membranes made of phospholipids with a thickness of 7 to 8 nm. For animal cells, the outside of the membrane is in contact with the external environment. Its main function is to selectively exchange substances, absorb nutrients, excrete metabolic waste, and secrete and transport proteins. ^[1]

The cell membrane is a barrier that prevents extracellular material from entering the cell freely. It ensures that

The cell membrane has important physiological functions. It not only enables the cell to maintain a stable metabolic intracellular environment, but also regulates and selects substances in and out of the cell. Cell membrane through

(1) Separation, formation of cells and

1.E. Overton 1895 found that all substances that are soluble in fat can easily penetrate the cell membrane of plants, and those that are not soluble in fat do not easily penetrate the cell membrane, so it is speculated that the cell membrane is composed of continuous lipid substances.

Water-soluble substances are difficult to pass through the plasma membrane

2. E. Gorter & F. Grendel 1925 extracted the lipid component of human red blood cell plasma membrane with an organic solvent, spread it on the water surface, and measured the area of the membrane lipid doubled as the cell surface area. Molecular composition.

3. J. Danielli & H. Davson 1935 proposed the sandwich model

4. JD Robertson 1959 proposed the unit film model

Structure of red blood cell membrane

5. SJ Singer & G. Nicolson 1972 According to the research results of immunofluorescence technology and freeze etching technology, based on the "unit film" model, a "flow mosaic model" is proposed. Emphasize membrane fluidity and asymmetry of membrane protein distribution.